Research And Design Of Broadband VCO Based On Ring Architecture

Voltage-Controlled Oscillator(VCO)is the core part of Phase-Locked Loop(PLL)and wireless communication system.The phase noise,frequency range and other parameters of VCO not only play a decisive role in the PLL performance,but also influence the function of the whole wireless communication system.With the development of integrated circuits,there are more and more demands for the oscillator with low power consumption,low noise and high frequency.Many scholars were attracted in the research of low power,low noise,high frequency and high performance oscillator structure.With this background,a wide-band VCO based on Ring architecture was designed.Firstly,the research background and development status of VCO were introduced.The oscillation principle,classification and main parameters of VCO were also described.And the advantages and disadvantages of ring oscillator and LC VCO were compared.Secondly,the causes and classification of oscillator noise were analyzed.Then,three noise analysis models and methods were adopted to reduce phase noise.Based on TSMC 65 nm technology,the ring oscillator circuit with new cross feed forward structure was designed,which includes bias circuit,delay unit and buffer.The phase noise was reduced by using the capacitance filter technique.The frequency modulation linearity was optimized with the linear current produced by the source pole negative feedback circuit.Thus the performance of VCO improved.In addition,the deep N-well isolation was adopted in the VCO layout to minimize substrate noise.The ring oscillator was designed based on TSMC 65 nm technology.The transient state,frequency characteristic and phase noise of ring oscillator were analyzed by the Spectre RF software of Cadence Company.The simulation results show that the tuning range of output frequency is 0.2GHz~3.8GHz,the current consumption is 4.6mA at 1.2V supply voltage,and the linearity is good.When the center frequency is 2.4GHz,the phase noise is-93.47dBc/Hz@1MHz.Then the layout of the VCO is designed by Virtuoso Layout Editor.The layout area is 70?m×81?m.The post simulation is carried out and the results show that the results are consistent with the pre-simulation results.Finally,this Ring VCO was applied in PLL.The circuit design,simulation analysis and layout design of PLL were completed,andthe simulation results show that the designed Ring VCO meets the requirements,and verify the importance of Ring VCO in PLL.